It is desirable for end-of-car cushioning devices under certain operating and train handling conditions to have a so-called reserve capacity adjacent the end of the buff travel particularly if the cushioning device is restricted at a relatively low force level which is desirable for cushioning of relatively low forces. Some prior art cushioning devices have a restricted flow adjacent the end of the buff travel which is obtained by a restricted metering orifice.
U.S. Pat. No. 4,040,523 dated Aug. 9, 1977 and entitled "Railway Car Cushioning Device" discloses an end-of-car cushioning device having a piston separating a cylinder into a high pressure chamber and a low pressure chamber with openings through the piston receiving a metering valve in each of the openings. The metering valves are set to open at a predetermined force level and are set to close at a predetermined force level. All of the metering valves are set to open and close at the same force level and this arrangement has been found to operate effectively with the high pressure and low pressure chambers having a mixture of gaseous and liquid fluid therein under a preload fluid pressure.